This invention relates to apparatus for applying a band (as defined hereinbelow) to a container. The invention also relates to methods of applying such a band to a container.
It is frequently desirable for a manufacturer of products sold in containers having removable lids to apply some kind of seal to the lid, so that the ultimate purchaser or user of the product will be assured that the container contents have not been tampered with, following the application of the seal. In the food industry, one kind of seal commonly employed comprises a length of tubular heat-shrink material which is placed over the container lid and extends over the container for at least part of the length thereof, the heat-shrink material then being shrunk by the application of heat whereby the container lid may be removed only by destroying the shrunk material. Removal of the shrunk material may be facilitated by perforating the material prior to its application to a container, so as to give a line of weakness along which the material may more readily be torn.
A seal formed from tubular heat-shrink material as described above is commonly referred to as a "band" when applied to the upper part of a container adjacent the lid, as well as over the lid itself. If however the material covers the greater part, or even the whole, of the container then such material is commonly referred to as a "sleeve". A sleeve may be used primarily for decoration or carrying information, but if it covers the lid as well, then it may also serve as a seal. In this Specification, the term "band " is used throughout though it is to be understood that this is intended to embrace to all kinds of tubular heat-shrink bands and sleeves, irrespective of the length of the container covered thereby.
A known form of apparatus for applying a heat-shrink band to a container and its lid is described for example in U.S. Pat. No. 4,562,684 (Dreher). This apparatus comprises a wheel carrying a plurality of reciprocating mechanisms arranged to feed a predetermined length of tubular material over a container top each time a container is located at a banding station, there being a guillotine to sever a lengths of the material for picking up by the mechanisms on the wheel. The reciprocating mechanisms grip the material when in a folded-flat condition, and then open it out by separating, in order to allow the material to be fitted over a container top.
A disadvantage of the apparatus described above is that since it includes several reciprocating parts, its speed of operation is significantly limited thereby. Moreover, the reliability of operation is not that high, and mis-feeds are frequently encountered for instance because a cut band has not sufficiently been opened out to receive a container top. The mis-fed band must then be cleared before the apparatus may continue to operate, lowering the through-put. It is a principal aim of the present invention to address these short-comings of the known apparatus.